Power conversion devices are typically built to perform prescribed functionality and set to perform the functions up to specified limits of the device. A simple example of a power conversion is the DC to AC power transfer of an inverter. The inverter is designed to efficiently convert power from a DC source to an AC form. The various components of power conversion devices have limits as to how far they can be stressed. The stresses may include thermal, voltage, current, physical, and the like. For the inverter to ensure it will not be damaged, monitoring and control methods are often utilized to report how close the inverter is to hitting these limits and, if reached, to ensure the inverter can protect itself from damage by shutting down, limiting current, changing modes, or any number of other self-limiting means. Inverters may also limit the amount of AC current they can produce to ensure this maximum capacity limit is never exceeded.
In more complex devices, such as an uninterruptable power supply (UPS), there may be more than one type of function required and therefore multiple capacity limits to report and measure. For a UPS, one dimension may be the amount of power being processed from the system, while another dimension may be the amount of battery run time available given the current loading and state of charge for its battery system.
A common requirement for the systems discussed above is to define the resource capacity dimensions and to report on how much of that capacity is being utilized, or, inversely how much capacity is available. In some instances, capacity limits can be prioritized to ensure the customer received the performance relevant to their needs. For example, a customer of a UPS may always want 10 minutes of runtime when batteries are fully charged, e.g., a run time priority. In this example, the UPS may alarm below its 100% load capacity if the load increases to a point where the 10 minutes cannot be guaranteed. Conversely, the customer may want to make sure the maximum amount of load can be attached to the UPS regardless of runtime, e.g., a power priority.
As new power conversion products emerge and increasing functionality can be delivered from a single unit, understanding the resource capacity dimensions, interrelationships, measurement and safe limitation becomes complex. Power conversion devices may be used to interact with the electrical power utility grid. For example, conventional power conversion devices are known that are coupled to an electrical utility grid that have multiple functions, e.g., a multi-function power regulator or unified power flow controller (UPFC). Another category of conventional devices, known as active filters, may measure, report and limit resource capacity typically based on current or voltage limits at higher order harmonic frequencies. Conventional active filters are used to improve power quality as it relates to current and voltage distortion.
The conventional multi-function power regulator or UPFC discussed above typically includes a synchronous compensator (STATCOM), or shunt converter, and a static synchronous series compensator (SSSCS), or series converter, connected to the electrical utility grid. The multi-function power regulator may be used to improve the power quality on the electrical utility grid by providing voltage and reactive power regulation. The shunt converter of a conventional multi-function power regulator may perform voltage regulation on the DC bus and voltage-ampere-reactive (VAR) regulation while the series converter may provide voltage regulation. The shunt converter functions and the series converter functions consume resources, inter cilia, RMS current, peak current, RMS voltage, respectively, which each have a resource capacity limit.
Conventional multi-function power regulators typically rely on setting hard limits for the resource capacity limits to prevent damage of the shunt converter, the series converter, and other components of the multi-function power regulator. Additionally, conventional multi-function power regulators typically rely on separate active filters discussed above to measure, report, and provide a limit capacity. However, to date, conventional multi-function power regulators have not been combined with active filters.
Thus, there is a need for a multi-function regulator that is able to provide operational priority and resource allocation to one or more of the shunt converter functions and/or the series converter functions and which can enable graceful scaling back of one or more functions that have reached a resource capacity limit to prevent damage to the various components of the multi-function power regulator.